Advances in Methanol Production and Utilization, with Particular Emphasis Toward Hydrogen Generation Via Membrane Reactor Technology
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membranes Review Advances in Methanol Production and Utilization, with Particular Emphasis toward Hydrogen Generation via Membrane Reactor Technology Francesco Dalena 1, Alessandro Senatore 1, Marco Basile 2, Sarra Knani 3, Angelo Basile 4 and Adolfo Iulianelli 4,* 1 Chemistry & Chemical Technologies Department, University of Calabria, Cubo 15/D, Via P. Bucci, 87036 Rende, CS, Italy; [email protected] (F.D.); [email protected] (A.S.) 2 Department of Ambient, Territory and Chemical Engineering, University of Calabria, Cubo 44/A, Via P. Bucci, 87036 Rende, CS, Italy; [email protected] 3 Laboratoire de Chimie des Matériaux et Catalyse, Département de Chimie, Faculté des Sciences de Tunis, Université Tunis El Manar, Tunis 2092, Tunisia; [email protected] 4 Institute on Membrane Technology of the Italian National Research Council (CNR-ITM), Via P. Bucci, c/o University of Calabria, Cubo 17/C, 87036 Rende, CS, Italy; [email protected] * Correspondence to: [email protected] Received: 11 September 2018; Accepted: 14 October 2018; Published: 18 October 2018 Abstract: Methanol is currently considered one of the most useful chemical products and is a promising building block for obtaining more complex chemical compounds, such as acetic acid, methyl tertiary butyl ether, dimethyl ether, methylamine, etc. Methanol is the simplest alcohol, appearing as a colorless liquid and with a distinctive smell, and can be produced by converting CO2 and H2, with the further benefit of significantly reducing CO2 emissions in the atmosphere. Indeed, methanol synthesis currently represents the second largest source of hydrogen consumption after ammonia production. Furthermore, a wide range of literature is focused on methanol utilization as a convenient energy carrier for hydrogen production via steam and autothermal reforming, partial oxidation, methanol decomposition, or methanol–water electrolysis reactions. Last but not least, methanol supply for direct methanol fuel cells is a well-established technology for power production. The aim of this work is to propose an overview on the commonly used feedstocks (natural gas, CO2, or char/biomass) and methanol production processes (from BASF—Badische Anilin und Soda Fabrik, to ICI—Imperial Chemical Industries process), as well as on membrane reactor technology utilization for generating high grade hydrogen from the catalytic conversion of methanol, reviewing the most updated state of the art in this field. Keywords: methanol; steam reforming; water gas shift; partial oxidation; membrane reactors; hydrogen 1. Introduction In the last century, fossil fuels represented the main source of energy production. These feedstocks are not renewable, are limited and, consequently, are responsible for an instable global market, which leads to a corresponding instability in fuel price. Moreover, fossil fuel exploitation is considered primarily responsible for greenhouse gas (GHG) emissions, contributing to the increase in global warming. Today, the most viable options for the exploitation of fossil fuels for power production result from hydrogen and methanol. The use of hydrogen appears very promising, as it shows the highest energy content per unit of weight (142 kJ/g) over any other known fuel and, furthermore, it is environmentally safe [1]. However, the key issues for wide hydrogen utilization as a new energy Membranes 2018, 8, 98; doi:10.3390/membranes8040098 www.mdpi.com/journal/membranes Membranes 2018, 8, x FOR PEER REVIEW 2 of 26 Membranes 2018, 8, 98 2 of 27 environmentally safe [1]. However, the key issues for wide hydrogen utilization as a new energy carrier are represented by its purification costs and by the difficulties linked to the infrastructure for itscarrier storage are representedand transportation. by its purification costs and by the difficulties linked to the infrastructure for its storageBy contrast, and transportation. methanol is easily stored and transported and can be used as a convenient hydrogen carrier.By It contrast, is also particularly methanol is useful easily storedin the andchemical transported industry and as cana solvent be used and as aas convenient a C1 building hydrogen block forcarrier. producing It is also intermediates particularly useful and in synthetic the chemical hydrocarbons, industry as aincluding solvent and polymers as a C1 building and single-cell block for proteinsproducing [2,3]. intermediates In vehicle andtransportation, synthetic hydrocarbons, methanol can including be mixed polymers with conventional and single-cell petrol, proteins without [2,3]. requiringIn vehicle any transportation, technical modification methanol can to bethe mixed vehicl withe fleet. conventional In fact, most petrol, methanol-fueled without requiring vehicles any currentlytechnical modificationuse M85 fuel, to which the vehicle represents fleet. Ina mixt fact,ure most containing methanol-fueled 85% methanol vehicles and currently 15% unleaded use M85 gasolinefuel, which [4]. represents a mixture containing 85% methanol and 15% unleaded gasoline [4]. Approximately 65%65% of of methanol methanol worldwide worldwide is consumedis consumed for thefor productionthe production of acetic of acid,acetic methyl acid, methyland vinyl and acetates, vinyl acetates, methyl methyl methacrylate methacrylate (MMA), (MMA), methylamines, methylamines, metil-t-butil metil-t-butil etere etere (MTBE), (MTBE), fuel fueladditives, additives, and otherand other chemicals. chemicals. The remainingThe remain portioning portion is converted is converted into formaldehydeinto formaldehyde and other and otherproducts products [3,5,6 ],[3,5,6], as illustrated as illustrated in Figure in Figure1. 1. 35 30 25 20 15 10 5 % of the worldwide methanol conversion methanol worldwide the of % 0 l e e id A E e rs in d c M B u e m hy A T F h a e c M M t il ld ti O th a ce e m A M or F FigureFigure 1. 1. ProductsProducts coming coming from from methanol transformation. A number of technologies were developed over the years to produce methanol, including several feedstocks, such as natural gas, coal, and biomass or CO —the latter directly recoverable from the feedstocks, such as natural gas, coal, and biomass or CO2—the latter directly recoverable from the atmosphere [3,7]. [3,7]. From an historic point of view, methanol production processes took place before before the the 1660s (by Robert Boyle). An importantimportant contributioncontribution to to its its development development was was by by Paul Paul Sabatier, Sabatier, who who carried carried out out the thehydrogenation hydrogenation of a largeof a large variety variety of functional of functional groups groups by metal-based by metal-based catalysis catalysis [8]. Methanol [8]. Methanol synthesis synthesiswas performed was byperformed BASF (Germany) by BASF in 1923,(Germany) developing in a1923, metal-based developing catalytic a hydrogenationmetal-based catalytic process hydrogenationat high pressure process [9]. The at high BASF pres processsure [9]. has The then BASF been process utilized has since then 1927 been by utilized both DuPont since 1927 and theby bothCommercial DuPont Solvents and the CorporationCommercial inSolvents the USA, Corporat representingion in the the start USA, point representing in the methanol the start production point in theindustry methanol and remainingproduction the industry dominant and technologyremaining the for overdominant 45 years technology [10]. for over 45 years [10]. Successively, in in the 1940s, the SwissSwiss LonzaLonza CompanyCompany producedproduced methanolmethanol industriallyindustrially from electrolytic hydrogen and CO , the latter derived from Ca(NO ) synthesis. The reactant gas electrolytic hydrogen and CO2, the2 latter derived from Ca(NO3)2 synthesis.3 2 The reactant gas purification frompurification nitrous from vapors nitrous was vaporsthen developed was then by developed Natta (Italy) by Natta and (Italy)combined and with combined the methanol with the synthesis methanol synthesis from CO and H [11]. from CO and H2 [11]. 2 Membranes 2018, 8, x FOR PEER REVIEW 3 of 26 Membranes 2018, 8, 98 3 of 27 The successive development of the steam methane reforming (SMR) reaction, able to generate syngas (aThe mixture successive of H development2, CO, and CO of2 the) combined steam methane with active reforming Cu/ZnO (SMR) catalysts, reaction, ablemade to it generate possible to operatesyngas at milder (a mixture conditions, of H2, CO, such and COas 3002) combined °C and with100 bar. active This Cu/ZnO was the catalysts, core of made the it“ICI possible process”, proposedto operate in 1966 at milder [3]. conditions, such as 300 ◦C and 100 bar. This was the core of the “ICI process”, proposedIn 1973, induring 1966 [3the]. oil embargo proclaimed by the Organization of Arab Petroleum Exporting CountriesIn in 1973, the duringUSA and the Th oile embargoNetherlands, proclaimed the interest by the toward Organization methanol of Arab exploitation Petroleum as Exporting an alternative automobileCountries fuel in thewas USA particularly and The Netherlands, intense, even the interestthough toward it was methanoldefinitively exploitation banned asafter an alternative the 1990s due automobile fuel was particularly intense, even though it was definitively banned after the 1990s due to to the harmful methanol combustion products negatively affecting the ozone layer. In the same the harmful methanol combustion products negatively affecting the ozone layer. In the same period, period, methanol market demand grew